This past June, we noted that Instagram hit a big milestone: 5 million users. At the time, the total number of photos shared on the service was at 95 million, and given the rate of growth, they expected to pass 100 million shortly. Well, they missed pointing out that milestone, but today, not even two months later, they’re pointing out another one: 150 million photos.

That’s 150 million photos uploaded to Instagram in just the 9 months since the app launched. For comparison’s sake, it took Flickr nearly two years to hit 100 million total photos on their service. Incredibly, Instagram is now seeing 1.3 million photos uploaded each day — that’s a rate of 15 photos per second.

The service is now well past 7 million users, Instagram co-founder Kevin Systrom tells us. Again, that’s up over 2 million in under 2 months. Without any sort of strategic promotions, they’re grown to become a mainstay in the top 25 free app in Apple’s App Store.

Yes, Flickr may now be well past 5 billion photos, and Facebook can see 750 million photos uploaded in one crazy weekend, but remember that Instagram is still only available on one platform: iOS. Every single one of those 150 million photos has been uploaded from an iPhone (and to a much lesser extent, iPod touches and iPads). You can’t yet use Instagram from any other devices, and you can’t even upload photos from your computer. And while Android support will come, the experience is going to remain predominantly a mobile one, Systrom says.

One more crazy stat: Systrom says that of the 150 million photos, 80 percent have had filters applied to them. And of the remaining 20 percent, plenty of those originate from other iPhone camera apps with their own filters.